No. No-one knows that drinking, smoking or over-eating are bad for you OP 
Or everyone knows perhaps.
But maybe their priority at the moment isn't to improve their health or fitness to stave off COVID which they may or may not catch and may or may not become very unwell from at some point in the future.
But just to get through their today which is definitely happening and definitely happening right now. And 'today' for many will be pretty fucking stressful and many are literally taking it one day at a time.
There's an awful lot of head tilting faux 'not understanding' at the moment when it's NOT 'not understanding', it is taking the opportunity to be sanctimonious, smug and judgemental.
"You're worried about COVID because you're FAT? Well that's weird, i'd have been worried before, why weren't you worried about being FAT before? its your gross fatness that will kill you, not COVID, how strange one worries you and not the other" .Head tilt.
Also not giving a shit about other lives and how different or harder than yours they may be. "I just don't understand why you'd drink more now when alcohol does bla bla bla" Head tilt.
Chronic MH problems, living alone and struggling with the isolation "but don't you have a 'phone OP? I'm loving not having people pop in all the time intruding on our family time, surely you can just talk to people on the 'phone, it's very easy to keep in touch with friends and family without seeing them". Head tilt.
Ad nauseum.